New research presented at the American Heart Association’s 2025 Scientific Sessions has linked long-term use of melatonin in people with insomnia to a higher risk of heart failure. The study, which reviewed five years of health records for more than 130,000 adults diagnosed with insomnia, compared those who took melatonin for at least a year with those who did not.
Results showed that about 4.6% of long-term melatonin users developed heart failure, compared with 2.7% of nonusers — a nearly 90% higher risk. Melatonin users were more than three times as likely to be hospitalized for heart failure (19% vs. 6.6%). Over five years, nearly twice as many melatonin users died from any cause compared with nonusers (7.8% vs. 4.3%).
“Melatonin supplements are widely thought of as a safe and ‘natural’ option to support better sleep, so it was striking to see such consistent and significant increases in serious health outcomes, even after balancing for many other risk factors,” said Ekenedilichukwu Nnadi, M.D., lead author of the study, in a statement.
The researchers stressed that the findings show an association, not proof of causation. However, they noted the consistency of the results gives reason to pause. The study identified melatonin users based on prescription records because in many countries it is a prescription drug. That means many over-the-counter users in the United States may have been misclassified as nonusers, making it harder to know the exact size of the difference.
Chronic insomnia is itself linked to a higher risk of heart problems, including heart failure. People who rely on melatonin for more than a year may have more severe sleep disruptions, and melatonin use could be an indicator of poor sleep health rather than the direct cause of heart problems.
Experts have long warned about unknown safety effects of melatonin. The new research gives more reason to proceed with caution. Short-term use of appropriately dosed melatonin may help with occasional jet lag, but the study suggests it is not a tool for nightly long-term use.
For those seeking alternatives, improving sleep hygiene — such as avoiding late-night alcohol, keeping the room dark and cool, and reducing screen time — is a good starting point. Another option is magnesium, an essential mineral that many people do not get enough of through diet. Low magnesium levels can contribute to heightened stress, muscle tightness, restless sleep, and mood shifts. Taking magnesium before bed may help the body and mind relax by activating receptors for GABA, a neurotransmitter that quiets an overactive nervous system and promotes calm, helping people fall asleep and stay asleep through the night.
The study is preliminary, but it suggests that long-term nightly use of melatonin may carry more risks than previously thought. Short-term use, good sleep habits, and supportive nutrients like magnesium remain safer ways to improve sleep naturally.
